The present invention relates to an electrical bussing and jumper assembly and, more particularly, to an electrical bussing and jumper assembly for use with electrical switching devices in a panelboard for distributing current to a plurality of branch circuits.
Electrical bussing and jumper assemblies for use in panelboards are very well known to these skilled in the art. One very common type of bussing and jumper assembly, of a three-phase type, employs a plurality (e.g., three) of elongated flat metal bus bars of rectangular cross-section (e.g., 3/16-1/4 inch thick) arranged in parallel and spaced from each other by predetermined distances related to the current rating of the assembly. A plurality of discrete metal jumper bars are bolted to the bus bars transverse to the lengths of the bus bars for connection to electrical devices such as circuit breakers, the jumper bars being spaced apart from each other through varying lengths of insulating sleeves (e.g., of polyvinyl chloride) made to surround one or more of the bus bars.
The above-described type of bussing and jumper assembly operates in a generally satisfactory manner. However, it has a number of disadvantages. A primary disadvantage is that the jumper bars, by virtue of being discrete elements, must be bolted onto the bus bars. The bolted connections may loosen or the bolts may not be tightened correctly during assembly, leading to poor heat dissipation and reduced efficiency and reliability. Further, the bolting on of the jumper bars and the cutting and installation of insulating sleeves of different lengths are costly labor operations, increasing the overall cost of the assembly. The use of insulating sleeves as described hereinabove also generally requires that the bus bars be spaced relatively widely apart, with the result that the finished assembly is not as rigid as might otherwise be the case. A further disadvantage of the above-described assembly is that heat produced during use of the assembly is conducted away from the assembly to adjoining elements (sub-pan, etc.) by radiation rather than distributing and dissipating the heat in the manner of a heat sink. This factor is significant when it is considered that excessive heat is a common cause of panelboard failure.